1. Field of the Invention
The invention relates to instrument flight method and apparatus for preventing an aircraft pilot from viewing outside his aircraft during instrument control flight instruction, and more particularly, to a pair of flight glasses which facilitates simulation of inflight vertigo.
2. Description of the Prior Art
In the area of inflight training, a student pilot must be trained to fly blind in bad weather. Pilots are required to have a minimum number of hours of flight instruction under simulated blind flying conditions before receiving a private or commercial license, or an instrument rating or military rating to fly aircraft. Such training is a necessity to pilots who plan to, or suddenly or inadvertently, fly into bad weather conditions.
Flight training hoods, goggles, glasses, and the like, have been designed to limit the wearer's field of view to only the instrument panel and immediate cockpit area. Such view limiting devices generally include elongated structures surrounding the pilot's line of vision for constriction thereof, blocking side and upper peripheral sight.
Some prior art flight hoods do not totally enclose or mask the wearer's line of vision in order to provide a safety factor which insures that the pilot can direct his vision outside the craft in the case of an emergency. However, to accomplish this factor, the hood's elongated structure extending in front of the operator's face becomes awkward and clumsy during flight and may cause eye straining or neck fatigue to support such apparatus. Also, the instructor must depend upon the wearer's trustworthiness during a testing and learning situation to purposefully keep his head substantially level so that the outside references are not in view.
Also, where the pilot inadvertently views outside of the aircraft, he would transition to VFR (visual flight rules) and must immediately transition back to IFR (instrument flight rules) as he looks back into the aircraft. This causes a disorientation to the pilot, promoting a time delay factor due to transition reorientation time. This psychological-type problem occurs with inadvertent viewing using the above-mentioned prior art devices.
Lens fogging-type devices have been considered in the flight hood art, but for the purpose of providing a visual contrast of a CRT display projected on the inside of a pilot's helmet, as described in an article of Rockwell International Corporation entitled "Variable-Transmittance Visor for Helmet-Mounted Display" by Dr. J. P. Dobbins. However, bi-state, lens fogging devices having a completely occluded vision state have not been considered nor utilized in the flight hood art because of a lack of mode of operation therein and because of the previously mentioned safety factor. Although such lens devices have been utilized in helmet-type gear, see for example U.S. Pat. No. 3,873,804 issued to M. Gordan on Mar. 25, 1974 and U.S. Pat. No. 3,409,909 issued to D. D. Scott et al on Nov. 12, 1968, the functioning of such devices are not compliant to the flight training hood art. Such devices are responsive to a bright flash of light that occurs during wearer viewing. However, in the flight training environment all stimuli including the ambient light in the cockpit are constant, having no apparent abrupt stimulus occurring at the time the desired fogging should take place.
Therefore, it would be highly desirable to provide flight training glasses having the ease and convenience of an unawkward structure including the quickness of an automatic lens system in which the lens would instantaneously operate in relation to the wearer's positioning of his line of vision.